Medical needles, such as needles for injection and lancets, that have been developed in recent years include less invasive products which are unlikely to produce pain or an unpleasant feeling as disclosed in Patent Document 1, for example. As depicted in FIG. 25, a skin-piercing element 50 disclosed in Patent Document 1 is provided with a distal portion 51 and a proximal portion 52, the distal portion 51 being formed to have a sharp end that is penetrable into a living body. As a fluid pathway 53 runs from the distal portion 51 to the proximal portion 52, a physiological sample collected in an opening 53a in the distal portion 51 of the fluid pathway 53 is guided to the proximal portion 52 due to a capillary force.